It depends on how far you are out of school. Generally under the 'education' section, applicants include both academic honours as well as extra-curricular activities, so these are generally relevant. Experiences before university are generally less so, however.
All writing is only as effective as its effect on the reader it is intended for. So yes, that is exactly right. Keep stuff relevant to business school in; take the irrelevant stuff out. Of course that only brings us back to your original question: is information from before college relevant? Which brings us to my answer: probably less so.